Abstract: Unexplained medical symptoms in functional medical illnesses present a challenging diagnostic dilemma for physicians. These conditions usually involve pain or pressure together with other symptoms which suggest a combination of biological and unexplained medical factors. Interstitial cystitis (1C), more recently labeled Painful Bladder Syndrome (PBS), is a prime example of this type of disorder. Recently, intense interest has focused on the psychological/psychiatric components of these disorders. In particular, our team has demonstrated that somatization disorder, when present, may influence the course and management of these functional medical syndromes. Patients with somatization disorder disproportionately consume clinicians' time and medical resources. Thus, understanding the role of somatization disorder in IC/PBS has the potential to yield clinical and economic benefits. In the present study, 120 patients with IC/PBS will be assessed for physical and psychological symptoms, medically unexplained symptoms, and somatization disorder, and they will also monitored over 12 months for temporal symptom patterns and outcomes. The study will demonstrate the proportion of patients with IC/PBS who also have somatization disorder and the degree to which these patients represent a significantly distinct IC/PBS subgroup with different illness presentation, progression, and outcome. Previous research by this team from similar studies of Irritable Bowel Syndrome (IBS) has generated highly useful information and will serve as a template for this research. The comparability of the findings of this study to previous work on IBS will help guide recommendations for modification of pharmacological and psychological interventions for this patient population. Recognition and appropriate management of somatization disorder in patients with IC/PBS has the potential to benefit a substantial proportion of patients with IC/PBS and inform future research. This proposed study truly investigates the interface of medicine and psychiatry in its approach to these disorders.